An example of known rotor for electric rotating machine is disclosed in JP2008-289329A (which will be hereinafter referred to as Patent reference 1). In the Patent reference 1, the rotor includes a rotor core which is formed by stacking plural magnetic steel sheet. The rotor core is sandwiched between a pair of end plates along a stacking direction of the rotor core, a pin is penetrated through the rotor core and the end plates and pressed with deforming at both end of the pin, and then the rotor core is held by the end plates.
According to the Patent reference 1, since a taper portion is formed at an outer circumference of the end plate by riveting or caulking or press-deforming the pin penetrated through the end plates, the taper portion provided at the rotor core side presses the rotor core and the rotor core is rigidly held by the end plates.
The two sides of the end plate of the electric motor disclosed in the Patent reference 1 have different directionality because of the taper portion formed on the one side face of the end plate. That is, when the end plates are attached to the rotor core with wrong directionality (i.e. a first side intended to face the stacking steel sheet and a second side opposite to the first side of the end plate is reversed and the second side of the endplate faces the rotor core) for placing the rotor core to be sandwiched between a pair of end plates, the outer circumference of the end plate is warped in a direction separating from the rotor core. Therefore, since press load does not act on the outer circumference of the end plate, holding force of the end plates acting on the rotor core may become insufficient by the centrifugal force caused by rotation of the rotor.
In another example of a known end plate different from the end plate of the Patent reference 1, the end plate has a flat plate-like shape without taper portion at on an outer circumference of the known end plate, and a pair of the end plates is normally pressed to the rotor core in a state where whole area of a side of the end plate contacts the rotor core. In this case, the end plate is arranged so that a face of the end plate which does not have a shear droop at the peripheral circumference of the end plate faces the side of the rotor core. Therefore, in this case as well, when the end plates are attached to the rotor core on the wrong side, holding force of the end plates acting on the rotor core may become insufficient by the centrifugal force caused by the rotation of the rotor.
A need thus exists for a rotor for electric rotating machine and a method for manufacturing the same which are not susceptible to the drawback mentioned above.